Changes between Version 7 and Version 8 of PackageEnvironments

Timestamp:

04/22/12 04:26:15 (13 months ago)

Author:

duncan

Comment:

add info about cabal-src

PackageEnvironments

@@ -93 +93 @@
  * https://github.com/creswick/cabal-dev/blob/master/README.md
 
-cabal-dev provides what it calls a sandbox for source packages and installed packages. `cabal-dev` has a command line interface that is very similar to that of `cabal`, so that it can be used as a drop-in replacement. It is implemented as a wrapper around the cabal-install command.
+`cabal-dev` provides what it calls a sandbox for source packages and installed packages. It has a command line interface that is very similar to that of `cabal`, so that it can be used as a drop-in replacement. It is implemented as a wrapper around the `cabal` command.
 
 For source packages, the sandboxing mean providing a local source package set that overrides the global package index. Tarballs can be added to this index. It provides a command `cabal-dev add-source /path/to/source/code` which generate an `sdist` snapshot of the given package and adds that tarball to the local source index.
@@ -111 +111 @@
  * http://hackage.haskell.org/package/cabal-src
  * https://github.com/yesodweb/cabal-src/blob/master/README.md
+
+`cabal-src` is intended to solve the problem that cabal does not know about the source versions of local packages, so it cannot use those source packages in its dependency planning. It has a command line interface that is very similar to that of `cabal`, so that it can be used as a drop-in replacement. It is implemented as a wrapper around the `cabal` command.
+
+Ordinarily, if you `cabal install` in a local directory, `cabal` knows only about the packages that are already installed, and the source packages available from hackage. It does not know about other local build trees. If you make a change to a package and install it, then go to build another local package then `cabal` will usually use the instance of the package that you just installed. However this is not always possible: to use consistent versions of dependencies it is sometimes necessary to rebuild a package. This is where the problem occurs, if `cabal` cannot see that source package then it cannot rebuild from that source. This is the problem that `cabal-src` tries to address.
+
+`cabal-src` address the problem by taking a snapshot of a source package and inserting it into `cabal`'s local source index. It modifies the `~/.cabal/config` file to tell `cabal` to look in this local index.
+
+This is in a way similar to what `cabal-dev add-source` does, but it does it for the user's default environment rather than for a local sandbox.
 
 == cabal-meta ==